1. Field of the Invention
This invention relates to a semiconductor light-emitting device comprising a metal electrode provided with openings. In detail, the present invention relates to a semiconductor light-emitting device improved in luminance properties.
2. Background Art
Recently, semiconductor light-emitting devices have been studied for application to displays or to lighting instruments such as lights and lamps. The semiconductor light-emitting device generally comprises electrodes and a semiconductor layer placed between them, and emits luminescence when electric current flows between the electrodes. Normally, the device has a pad electrode in ohmic contact with the semiconductor layer, and the luminescence is given off from the periphery of the pad electrode when the electric current flows. If used as a light or the like, the light-emitting device is preferred to be relatively large. However, enlarging the pad electrode is not effective in expanding the light-emitting part, and hence, practically a fine wire electrode is additionally put from the pad electrode along the semiconductor layer surface so that the light-emitting part can be expanded. On the other hand, if the fine wire electrode is extended, it generally has a problem of making the electrode structure complicated.
From the viewpoint of application to lighting instruments, it can be also considered to supply an enough amount of electric current for the devices to enhance the luminance intensity. In a conventional semiconductor light-emitting device comprising the pad electrode, the luminance intensity increases according as the electric current increases until a certain value but then the intensity reaches the peak at the certain current value. Even if the current increases more than that value, the luminance intensity does not increase but decreases. A large reason of this is because much electric current flows in the device to generate heat and the heat is not sufficiently cooled. Accordingly, in order to enhance the luminance intensity of a conventional device, it is necessary to cool the device sufficiently. To cope with this problem, it is proposed to provide a heat-sinking substrate on the bottom of the device. However, that is not very effective at present probably because the substrate is positioned too far from the heated part.
JP-A 2009-076361 (KOKAI) discloses that a metal electrode provided with openings can be employed in the semiconductor light-emitting device. However, this publication focuses on small light-emitting devices applicable to LEDs and the like, and hence is silent about large devices usable as lights and the like. Further, in the publication, there is no description of the above problems such as the heat generation and the luminance deterioration.